He will be in his Sedgefield constituency today, indicating that he is not planning big changes apart from confirming the expected appointment of Peter Mandelson as Britain's next European commissioner.

But he said: "We have just been publishing these five-year strategies and I want to see them through."

His remarks are certain to disappoint Mr Brown, who has become increasingly impatient to assume the Labour leadership.

If Mr Blair lasts another full term in Downing Street - his third - he will have been Prime Minister for 12 or 13 years.

He will become the longest continuous serving premier since Lord Liverpool, who served from 1812 to 1827, eclipsing the 11 years of his role model, Lady Thatcher.

Mr Blair began the press conference with a presentation which he claimed showed the Government was making "irreversible" progress in improving public services.

Graphs and charts produced by Michael Barber, the head of the No 10 delivery unit, showed the Government was making progress on reducing deaths from heart disease and cancer, had reduced NHS waiting times and was raising education standards.

They indicated only four areas where the Government had not improved on the situation when it came to power in 1997: robbery, gun crime, antisocial behaviour and rail punctuality.

Mr Blair said his first seven years as Prime Minister had shown for the first time in Labour's 100-year history "that you can combine a strong commitment to economic prosperity with a commitment to social justice".

"We have still got things to do. It is true that we have fulfilled what we said we would do in terms of improvement and investment in public services and so on, but there are still big challenges that remain and we want - I want - to see them through."

He denied that Armed Forces cuts announced by Geoff Hoon, the Defence Secretary, on Wednesday meant "swingeing" reductions in military capacity.

The Services were being "reconfigured" to make them better able to respond quickly and with flexibility to the threats facing Britain in the modern world, while the Government was investing record levels of money in the military.

While some ageing battleships and warplanes were being scrapped, other equipment - including two aircraft carriers and greater strategic lift capabilities - was coming on stream, said Mr Blair.

"Our Armed Forces need to be highly mobile, highly flexible. It is unlikely they will be called on to do what the Armed Forces would have been called on to do 60 years ago and defend this country in a traditional sense," he said.

Mr Blair indicated that he would resist moves by the European Commission to renegotiate Britain's rebate on its contributions to the EU budget, secured by Margaret Thatcher 20 years ago.

The rebate was there for a "good reason", because without it Britain's contributions would be "unfair".

He refused to give ground on Iraq, insisting that the intelligence he had received showed that Saddam Hussein posed a threat from weapons of mass destruction.

Mr Blair rejected suggestions that the omission from his September 2002 WMD dossier of intelligence agencies' caveats - which warned of the limitations of their knowledge - made the document misleading.

"I don't accept that people were misled, because I think if you read the Joint Intelligence Committee assessment, their judgments are absolutely clear," he said.

The "only conceivable conclusion" from the JIC's reports was that Saddam was a threat in relation to WMD.